Based on the potential energy function which considers the nuclear motion and isotopic effect of DTO (X1A1), the atomic and molecular reactive collision for O+DT has been studied by Monte-Carlo quasi-classical trajectory approach. It is shown that the reaction O+DT→DTO with a long-lived complex compound has no threshold energy at low collision energy, which agrees with the potential surface. When the collision energy is higher than 209.2 kJ·mol-1, the interchange reactions will start and then increase until DTO molecules are decomposed completely into D, T, O with the collision energy increasing. The interchange reactions O+DT(0, 0)→OD+T and O+DT (0, 0)→OT+D have corresponding threshold energies. The trajectories and collision section of interchange reactions show asymmetrical distribution which corresponds to the potential surface.